This non-provisional application claims priority to Korean Patent Application No. 2006-006213 filed on Jan. 20, 2006, and all the benefits accruing therefrom under 35 U.S.C. § 119(a), the content of which is herein incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a siloxane dispersant and a nanoparticle paste composition comprising the same. More particularly, the present invention relates to a siloxane dispersant having a structure including a head part having affinity for nanoparticles and a tail part having affinity for a polydimethylsiloxane (hereinafter, referred to as “PDMS”) resin, and a nanoparticle paste composition comprising the same.
2. Description of the Related Art
Quantum dots are nanometer-scale semiconductor materials exhibiting quantum confinement effects, and are widely used in a variety of electrical and optical devices, due to their superior physical, chemical and electrical properties.
For application to various devices, such quantum dots are usually mixed with a dispersion medium such as a conventional solvent or resin and are used in the form of a previously prepared paste. However, quantum dots exhibit a tendency to form aggregates because a cohesive force between particles is very strong from the viewpoint of the properties of the nanoparticles. As a result, formation of such aggregates may cause problems in that unique properties of the quantum dots cannot sufficiently be exerted. Therefore, selection of a dispersant to be used should be more carefully considered such that aggregation between nanoparticles does not occur in the solvent or resin.
Meanwhile, as conventional solvents for nanoparticles, there are known nonpolar organic solvents such as toluene, hexane and the like, and polar binder resins such as epoxy resins, PDMS resins, acrylic resins and the like. Among these materials, the PDMS resins, which have a structure of siloxane-based backbones as a main chain, exhibit excellent properties such as high stability to heat, UV light and oxidants, superior transparency, relatively low refractivity and high insulation capacity, and therefore are very useful for application to electronic materials, particularly optical materials.
However, since the dispersants, used in synthesis of nanoparticles, are composed of hydrocarbon-based chains that are nonpolar, surfaces of nanoparticles show poor affinity for PDMS resins. It is therefore impossible to successfully disperse nanoparticles without modification of surface properties thereof. As such, there has been an urgent need for the development of a novel type of a dispersant that can be easily dispersed in the PDMS resins without causing aggregation or precipitation.
In this connection, U.S. Pat. No. 6,645,569 discloses a technique of improving dispersibility of nanoparticles for ink jet printing, involving introduction of a polyethylene oxide group or trimethyl ammonium group into a siloxane backbone. U.S. Pat. No. 5,919,487 discloses a technique of improving dispersibility of nanoparticles involving coating nanoparticles via introduction of a polyethylene oxide group or polypropylene oxide group into a siloxane backbone. However, unlike the present invention, these US patents do not involve functional groups that directly bind to nanoparticles.
In addition, Journal of Magnetism and Magnetic Materials 225 (2001) 47-58 discloses a technique of dissolving a cobalt precursor in poly[dimethylsiloxane-b-(3-cyanopropyl)methylsiloxane-b-dimethylsiloxane] to form cobalt nanoparticles, and then dispersing the thus-formed nanoparticles in the PDMS resin. This method does not particularly use a dispersant unlike the present invention, but instead uses a nitrile group as a functional group that binds to nanoparticles, which is distinctly different from the present invention.